1. Field of the Invention
The present invention relates to function generators, and particularly to a logarithmic and exponential function generator for analog signal processing.
2. Description of the Related Art
Logarithmic and exponential function generators are widely used in analog signal processing. An exponential function generator circuit produces an output waveform (current/voltage) that is an exponential function of the input waveform (current/voltage). Such a circuit is widely used in numerous applications, such as disk drives, variable gain amplifiers, automatic gain control circuits, medical equipment, hearing aids, and other analog signal processing and telecommunication applications.
On the other hand, a logarithmic function generator circuit produces an output waveform (current/voltage) that is a logarithmic function of the input waveform (current/voltage). Such a circuit is widely used in numerous applications, such as automatic-gain control loops, and in the design of analog-to-digital converters. Moreover, combining a number of exponential and logarithmic function generators, it is possible to design a multiplier circuit. Multipliers are versatile circuits with applications in signal processing, such as adaptive filters, modulators and neural networks. Inspection of the available exponential/logarithmic function generators shows that each circuit suffers from disadvantages, e.g., very limited input range, increased complexity, and the like.
Thus, a logarithmic and exponential function generator for analog signal processing solving the aforementioned problems is desired.